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Reducing Insecticide Use Among Resource-Poor Maize Farmers in Nicaragua



Field experiments were conducted and an extension program implemented to help resource-poor maize farmers in Nicaragua reduce their insecticide use. The field studies determined the impact of timing and level of infestation on the three important maize pests, Dalbulus maidis (DeLong & Wolcott), Spopotera frugiperda (J.E. Smith), and Diatraea lineolata (Walker) on maize yield. These studies differ from other studies in that they clearly separate the effects of timing and level of infestation. Early D. maidis infestation caused greater yield losses than late infestation. Infestation of S. frugiperda and D. lineolata during mid- to late-whorl caused greater yield reduction than early-whorl stage infestation. Damage functions for S. frugiperda infestation and maize yield were estimated with linear regressions. The regressions were used to calculate economic injury levels for S. frugiperda, which varied between 22 and 58% of the plants infested. Government subsidies on agricultural inputs declined from 100% subsidy in 1987 to 0% in 1991. After the removal of the subsidies, irrigated maize production was un-economical and eliminated. Irrigated maize production had provided a reservoir for the pathogens which cause maize stunting diseases, resulting in an epidemic in the late 1980s. By 1992, with the virtual elimination of irrigated maize, the incidence of stunting diseases declined sharply. A training program for 1,200 resource-poor maize farmers taught correct insect identification, the use on an economic threshold for S. frugiperda, the correct timing, dose, and application method of insecticides, and simple cost-benefit analysis of pest management. Maize production practices were monitored for three groups of farmers over three years: promoters, who received intensive training from extensionists and carried out demonstration plots, program farmers, who received training from promoters and visited the demonstration plots, and control farmers, who did not receive direct training from the program. After one year of training, chlorpyrifos use declined 71, 39, and 36% for promoters, program and control farmers respectively. After three years, maize yields did not change significantly, expenditures on insecticides declined by 60, 50 and 32%, net returns increased by 213, 32, and 9% for promoters, program and control farmers respectively.
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